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Patented Apr. 22, 1952 UNITED STATES PATENT OFFICE 2,7 -DIAMINO -9- (AMINOPHENTYL) PHENAN THRIDINIUM SALTS Leslie Percy Walls and Norman Whittaker, London, England, assignors to Burroughs Wellcome & 00. (U. S. A.) Inc., Tuckahoe, N. Y., a corporation of New York No Drawing. Application August 19, 1950, Serial No. 180,514. In Great Britain July 11, 1947 6 Claims.

Q-phenyl nucleus or in either or both of the fused rings with or without other substituents possess, in the form of their quaternary salts, a bactericidal, with, in some cases, a trypanocidal activity. The number of known compounds of this type which have been tested for possible clinical or veterinary use is considerable. However, the published results do not suggest such an interrelation between chemical structure and therapeutic activity in this large class of chemical compounds as to enable the structure of highly potent drugs to be predicted and indeed up to the present time not more than two or three members of the entire class have been used in veterinary medicine. Of these the compound of outstanding practical importance prior to this invention was 2:7 diamino-9-phenyl-10-methyl phenanthridinium bromide (see Specification No. 587,673).

It has now unexpectedly been found that the hitherto unknown phenanthridines 2 :7-diamino- 9 p-aminophenylphenanthridine and 2:7-diamino-9-m-aminophenylphenanthridine possess, in the form of their quaternary salts, unexpectedly superior properties, being markedly more active in T. congolense infections than the said Q-phenyl analogue and also possessing activity of a high order against T. rhodesiense.

Tested against T. congolense infections in mice, 2,7 diamino-9-p-aminophenyl-l0-methyl phenanthridinium chloride is 1.5 times as potent as the known 2,7 diamino-9-phenyl-10-methylphenanthridinium bromide is significantly less toxic, the most reliable values obtained with groups of the same mice being, by the intravenous route, LD50=10 mg./kg. body weight as against 7 mg./kg. Since the margin of safety between the curative and the toxic or irritating doses of phenanthridinium salts is not in general so great a might be desired, the new compound appears to have a very definite superiority over that previously known. The potency against T. rhodesz'ense (a parasite of man) is in the order of ten times that of the older substance, but since the latter has not been adjudged safe for human therapeutics it is not yet clear whether the subject of the present invention can be administered to human ubjects.

The new compounds of the present invention may be produced by methods already well known per se. The method of manufacture, the subject of co-pending British patent application No.

cipally chloride ion).

18,519/47, in which 2-amino-4:4-dicarbethoxyamino-diphenyl is used as starting material, represents a very convenient route but there can also be employed other methods of the general type which involve the production of an inter-,- mediate:

(where X represents a nitro group, an acylamino group or a carbalkoxyamino group and Y is a paraor meta-substituent in the form of a nitro or acrylamino group) by methods known for the production of phenanthridine containing one or more of the stated substituents, followed-by conversion into the required quaternary salts. Whichever method be employed, it is preferred toquaternise prior to the step of converting X and Y into amino groups and thus to effect such conversion in an intermediate quaternary salt.

The quaternary salts of the present invention possess the general formula:

wherein X and Y are different radicals selected from the class consisting of the amino group and hydrogen and A represents the anion of an acid. Specific examples are the halides and alkyl sulphates, in particular the chloride and the corresponding bromide and methylsulphate. Upon injection into the body of an animal the anion becomes dispersed among the vastly larger quantities of the anions of the body fiuids (prin- Consequently the identity of A is of no consequence in therapy unless inherently of very high toxicity. The anions of all non-toxic acids are therefore considered to be equivalent for the purposes of this invention. As a matter of fact, the presence of even the anion of a toxic acid such as HCN would hardly matter since the amount of cyanide ion introduced in a curative dose of this phenanthridinium salt would not be dangerous. The nature of the anion determines solubility, and thus the anion may be selected according to requirement in this 3 respect. For parenteral injection the chlorides are very suitable.

The present invention is illustrated by the following examples in which the temperatures stated are on the centigrade scale.

Example 1 Equimolecular quantities of 4:4-dinitro-2- amino-diphenyl and p-nitro-benzoyl chloride were condensed in boiling nitrobenzene. After evolution of hydrogen chloride had ceased, the solution was cooled to allow separation of 2-pnitrobenzamido 4:4 dinitrodiphenyl in almost quantitative yield. Recrystallization from aqueous pyridine furnished small yellow prisms, M. P. 234. (Found: C, 56.2; H, 2.9; N, 13.75. C19H12O7N4 requires C, 55.85; H, 2.95; N, 13.7%.) When this amide was refluxed in nitrobenzenephosphoryl chloride for several hours (B. P. 520, 273) 2:7-dinitro 9 pnitrophenylphenanthridine crystallized almost quantitatively in cream-colored needles; recrystallization from nitrobenzene gave a product, M. P. 356-358.

(Found: C, 58.6; H, 2.15; N, 14.35. C19H1006N4 requires C, 58.45; H, 2.6; N, 14.35%.) The foregoing powdered trinitro-compound g.) was suspended in alcohol (125 ml), concentrated hydrochloric acid (25 ml.) and crystalline stannous chloride (30 g.) added, and the mixture refluxed for 2 hours. After cooling the dark red solid was collected, dissolved in hot water, separated from unchanged trinitro-compound (1.1 g.), and then stirred into excess sodium hydroxide solution. 2:7-diamino-9-p-amino-phenylphenanthridine was thus precipitated as a yellow solid, which crystallized from alcohol in yellow plates, M. P. 245. (Found: C, 76.0; H, 5.45; N,

18.35. Cl9Hl6N4 requires C, 76.0; H, 5.36; N,

18.65%.) This base was extremely soluble in dilute acid aficrding intense carmine solutions. It was acetylated by acetic anhydride-acetic acid; on dilution of the solution thus obtained with water an orange gel formed, which was converted to a flocculent precipitate by the addition of ammonia. Crystallization of this produce from alcohol afiorded 2:'7-diacetamido-Q-p-acetamidophenylphenanthridine in cream-colored woollike needles, P. 312. (Found: C, 69.9; H, 5.65; N, 13.25. C25-H22O3N4 requires C, 70.4; H, 5.2; N, 13.15%.) A suspension of this compound (5 g.) in nitrobenzene (150 ml.) at 180 was treated with methyl sulphate (5 g.). The gum that separated was isolated by decantation and refluxed with alcohol (200 ml.). The 2:7-diacetamido 9 p acetamidophenyl -l0- methylphenanthridinium methylsulphate thus left undissolved was crystallized from methyl acohol in orange plates (2 g.), M. P. 248 (decomp.). Hydrolysis of this salt could be effected by refluxing with N-hydrochloric acid until a clear solution was obtained (several days); more conveniently and with less serious bumping the salt (0.4 g.) was heated in suspension in methyl alcoholic hydrochloric acid ml.) until all dissolved (ca. 6 hours) and then evaporated to small bulk. When neutralized with aqueous ammonia the 2 7-diamino-S-p-aminophenyl-IO-methylphenanthridinium chloride separated in dark purple prisms and was purified by recrystallisation from water, M. P. ca. 240 (with decomposition).

Example 2 was added to a solution of'2-amino-4:4'-biscar- This amide bethoxyaminodiphenyl (40 g.) in nitrobenzene (160 ml.) at 150. After one hour the solution was cooled, and microscopic needles of 2-mnitrobenzamido 4:4 biscarbethoxyaminodiphenyl then crystallised, which on recrystallisation from ethanol formed pale yellow needles (41 g.), M. P. 194 196 (slight eifervescence). (35 g.) and phosphoryl chloride (35 ml.) were heated for one hour in a bath at 130. The solution was then cautiously stirred into ice-cold 2N.NH4OI-I, care being taken to maintain an alkaline reaction. A solid was thus precipitated, which crystallised from aquepyridine in wool-like yellow needles of 2:7-biscarbethoxyamino 9 m nitrophenylphenanthridine, M. P. (with effervescence) 205-20'7 C., raised to 208.5-210.5 by recrystallisation. This substance was readily soluble in pyridine or acetone, but sparingly so in other common organic solvents. Its quaternary methylsulphate crystallised out, when solution of the base in nitrobenzene at 160 was treated with methyl sulphate. This salt is almost insoluble in. cold water, but dissolves sparingly in boiling water; it was purified by continuous extraction of the crude product with boiling water; on cooling, it crystallised in hair-like golden yellow needles, which darkened below 200, and decomposed rapidly at 200-210 (dependent on rate of heating). It was hydrolysed by heating it (3 g.) with sulphuric acid (6 ml. concentrated acid and 3 ml. water) at 135-140 C. for one hour. The solution was then cooled, and diluted with water to 30 ml. On cautious addition of ammonia (d. 0.885; 6 ml.) the acid sulphate crystallised in dark-red needles (2.1 g.), which decomposed ca. 220". When this sulphate was dissolved in N.HC1 and a little ammonium chloride added, 2:7-diamino-9-m-nitrophenyl-l0- methyl phenanthridinium chloride hydrochloride crystallised in transparent red plates. On neutralisation with ammonia a solution of this salt became deep purple in colour, and the quaternary chloride separated as a gum, which slowly crystallised in purple-black prisms.

The acid sulphate (2 g.) was dissolved in water (ca. ml.) and crystalline barium hydroxide added to neutralise. A suspension of ferrous hydroxide (from 15 g. crystalline ferrous sulphate and 15.5 g. crystalline barium hydroxide in ca. 100 ml. water) was then added at 100. Rapid reduction occurred and after 30 minutes at 100 the filtrate was collected, made just a1- kaline with ammonia, filtered from a slight precipitate, and evaporated to ca. 100 ml. Addition of ammonium chloride then caused 2:7-diamino- 9 m aminophenyl 10 methylphenanthridinium chloride to crystallise in purple-black prisms (1.2 g.), M. P. (decomp) 221. An extremely pure salt was obtained by filtering an aqueous solution through a short column of talc, which served to remove traces of iron.

We claim:

1. A compound of the formula wherein X and Y are different radicals selected from the class consisting of the amino group and hydrogen and A" represents the anion of a non-toxic acid. T

2. A salt of 2,7-11gmino-9-p-aminophenyl-10- methyl phenanthridiliium.

3. 2,7 diamino -9.-p-' aminophenyl -10- methyl 5 phenanthridinium chloride.

4. 2,7 diamino -9.- paminophenyl -l0- methyl phenanthridinium bi'omide.

5, 2,7 diamino -9 p aminophenyl -10- methyl phenanthridinium methylsulphate.

6. A salt of 2,7 10-methylphenanth PERCY WALLS. NORMAN WHITTAKE'R.

. l0 igimhxo-Q-m-amino-phenyl- 6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,397,391 Walls Mar, 2 6, 19-16 2,437,869 Walls Mar. 16, 1943 2,452,001 Walls Oct. 19, 1948 OTHER REFERENCES Walls et 2.1.: J. Chem. Soc. (London), January 1950. pp. 41-47. 

1. A COMPOUND OF THE FORMULA 